https://docs.splunk.com/Documentation/Splunk/8.0.2/Knowledge/SetupaGETworkflowaction
Define a GET workflow action
Steps
Navigate to Settings > Fields > Workflow Actions.
Click New to open up a new workflow action form.
Define a Label for the action.
The Label field enables you to define the text that is displayed in either the field or event workflow menu.
Labels can be static or include the value of relevant fields.
Determine whether the workflow action applies to specific fields or event types in your data.
Use Apply only to the following fields to identify one or more fields. When you identify fields, the workflow
action only appears for events that have those fields, either in their event menu or field menus. If you leave it
blank or enter an asterisk the action appears in menus for all fields.
Use Apply only to the following event types to identify one or more event types. If you identify an event
type, the workflow action only appears in the event menus for events that belong to the event type.
For Show action in determine whether you want the action to appear in the Event menu, the Fields
menus, or Both.
Set Action type to link.
In URI provide a URI for the location of the external resource that you want to send your field values to.
Similar to the Label setting, when you declare the value of a field, you use the name of the field enclosed by
dollar signs.
Variables passed in GET actions via URIs are automatically URL encoded during transmission. This means
you can include values that have spaces between words or punctuation characters.
Under Open link in, determine whether the workflow action displays in the current window or if it
opens the link in a new window.
Set the Link method to get.
Click Save to save your workflow action definition.

Reference:
https://www.edureka.co/blog/splunk-events-event-types-and-tags/

Explanation
The correct answer is B. Calculated fields can be chained together to create more complex fields.
Calculated fields are fields that are added to events at search time by using eval expressions. They can be used to perform calculations with the values of two or more fields already present in those events. Calculated fields can be defined with Splunk Web or in the props.conf file. They can be used in searches, reports, dashboards, and data models like any other extracted field1.
Calculated fields can also be chained together to create more complex fields. This means that you can use a calculated field as an input for another calculated field. For example, if you have a calculated field named total that sums up the values of two fields named price and tax, you can use the total field to create another calculated field named discount that applies a percentage discount to the total field. To do this, you need to define the discount field with an eval expression that references the total field, such as:
discount = total * 0.9
This will create a new field named discount that is equal to 90% of the total field value for each event2.
References:
About calculated fields
Chaining calculated fields